Various existing and new computing devices make use of high speed, volatile memory (e.g., dynamic random access memory, or DRAM) to hold operating instructions and data. Such devices include mobile phones, television set-top boxes, personal computer memory, and so forth. Increasingly computing devices are also including large amounts of relatively inexpensive nonvolatile NAND flash memory to store applications and data.
However, many existing DRAM-based computer devices are designed without the appropriate bus interfaces to support NAND flash memory; to support NAND flash memory requires a costly and lengthy redesign of the device chipset. Similarly, most NAND flash-based devices cannot simply add DRAM. Significant changes to a device's physical architecture are required to put flash memory into an updated model of what was a DRAM-based device, for example, or vice-versa.
While a combination of volatile and nonvolatile memory provides benefits in many situations, often the expense of redesigning a device chipset is too costly/risky for a vendor, whereby the vendor forgoes new features and business models that would be otherwise enabled by having volatile and nonvolatile memory in a device. Further, there is no straightforward way to use existing architectural models and, for example, update an existing DRAM-based device with NAND flash memory; e.g., an entire circuit board would need to be redesigned and replaced, instead of simply adding memory to or changing memory in an existing device (and updating software as appropriate). Moreover, there is a large difference in bus speeds between non-volatile and DRAM-based memory.